consumption
Share of i n d i v i d u a l sources in SE's
installed capacity
As of 31 December 1994
As of 31 December 1995
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
SE's share in covering SR consumption
GWh I
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Seismic characteristic of this region is a very low activity. From the historical point of view, we collected data from time period 1022 up to 1994. For the Mochovce site, the Komarno area is the most dangerous, with maximal historical earthquake is 8,5°.-of MSK - 64 scale: it is about 55 km from EMO site, south - west direction (Komarno area) (Fig.2). The attenuation law decreases the intensity from 6 MSK-64 to about 2,5. Another seismic area is ,,Middle Slovakian area"
(Kremnica, Banska Bystrica (7.5) and Dobra Voda (9) (Fig.3). But from this direction the attenuation is also about 2 of MSK-64 and 3,5 of MSK-64.
EMO site is located on the rock soil with volcanic layer (andesit). Characteristic shear wave velocity is between 2,000-3,000 m/s.
Seismic re-evaluation
The original design of Mochovce NPP did not follow the IAEA recommendation about the minimal seismic hazard. The requirements from today authorities are higher for NPP safety to external hazard and therefore some upgrading is required to a level generally accepted by the international community. Therefore, the seismic input SSE has been upgraded to ZPGA = 0.1 g for the estimation of the seismic resistance of buildings and equipment. In accordance with IAEA documents, the RLE has been defined as:
is O.lg (in horizontal direction), is 0.067g (in vertical direction),
is NUREG-0098 ground spectrum of absolute acceleration (median +lsigma) for rock site, resp. for shape site of next buildings.
This PGA is corresponding with an intensity 7° in MSK - 64 scale. For re-evaluation of reactor hall the Newmark's ground rock spectrum is applicable because the velocity of shear waves is higher than 1 100 m/s limit (Fig.4).
We used a less conservative method than used in formal design process. This fact was confirmed in the revised edition of POSAR - part Seismic Hazard.
The methodology ,,Seismic re-evaluation guide of Mochovce NPP structures and equipment Units 1 and 2" was prepared by Skoda Praha and Stevenson & Associates. The guideline of NPP Mochovce -Unit 1 and 2 - seismic re-evaluation is based on IAEA document ,,Technical guidelines for the re-evaluation programme of Mochovce NPP" from august 1995. This document
recommended for seismic re-evaluation of NPP Mochovce a SMA methodology and a special GIP procedure for the qualification of active safety related equipment. The SMA methodology defines the boundary seismic capacity of NPP as the whole. This methods studies the question whether the capacity of the already built plant exceeds the target earthquake input which was selected for review. Following the guidelines, we recalculated the floor response spectra to be used for the qualification of those structures, systems and components needed to bring the plant to a safe shutdown condition after an earthquake, and maintain it in a safe shutdown condition for certain defined period.
The main criteria for PWR reactor units are integrity of primary system. The plant must be capable to be brought and maintained in a cold safe shutdown condition during the first 72 hours following the occurrence of the RLE and seismic interactions prediction. The first step was based on the original design and 8 000 mechanical components (pumps, tanks, pipes) and about 15 000 electrical and I&C components (cables, cable traces, cabinets, etc.) were qualified.
The rest of structure and components, which are out of the safe shutdown equipment list, are not seismically resistant. At the present time equipment list is divided into two groups:
39
Komorno
cofrofDiiieci t>y SzefdaMtte
1.500 000
SCALE
10 0 10 70 X 4O SO t<m
LEGEND
O SITE O
O
rf--3.0-3.5 ,( = 3.5-4.0 yrf = 4.0-4.5 V! = 4.5-50 M = 5.0-5 5
M-5.5-6.0
EARTHQUAKES MAPS INTO A 150KM RADIUS FROM NPP
K)
a (ma~ )
_DESIGN tkSIS FOR MOCHOVCE
0,5 I
0,0-0,5
\/
/x.
Horizontal, innact
\r
re
o-—
a (ma )
Vertical impact
- Priority H (high) and L (low)
(H priority means - equipment's are needed to bee reinforced up-to start-up) (L priority means - equipment's can bee reinforced later or in the first outage)
At the and we collected the list of equipment's with approval protocols of seismic resistance based SQUG-GIP (HCLPF):
-recalculation -reinforcement -replacing as appendix of POSAR.
Seismic instrumentation
• Internal seismic instrumentation
In the basic design for NPP Mochovce, the plant was designed with a seismic shutdown system called SIAZ of Soviet production (System of Industrial Antisesmic Protection). His function was initiating a signal (as automatic reactor scram) for:
- Reactor Protection System - to initiate shutdown
- Safety system - to switch on the equipment's for aftercooling though the initiating schedule
- Alarm to Main Control Room
- Switching off crane and refuelling machine - Recording of the absolute acceleration versus time
SIAZ had nine triaxial accelerometers in three independent systems with independent electric power supply and two sets of them (totally 18 sensors). The output from seismic monitoring system is an active input for reactor protection system and for many other Safety systems. In the basic design the reference value of acceleration was assumed to be that measured by triaxial sensors located at the NPP foundation base. The triggering level is 0.0Ig and the initiating level is 0.05g.
• External seismic monitoring network
Monitoring of seismic activity at the site of NPP and near region is a standard activity in the world. It gives useful information of seismic sources and micro-earthquake capability.
The minimum monitoring period required to obtain meaningful data for seismo-tectonic interpretations is several years.
The system comprises of a network of 7 seismometer stations located within a radius of about 25 km from the Nuclear Power Plant at Mochovce. One of them is located inside the area of NPP about 600 m from Reactor Hall. Seismic instrumentation has been purchased from Lennartz Electronic (Germany) and GEMI (Czech Republic). The mounting of the seismograph stations were preceded by an extensive field survey and careful investigation of noise background.
The Seismic Monitoring Network System is currently operated and its data transferred, processed and analysed by Progseis Trnava and the Geophysical institute of Slovak academy of sciences, on a weekly basis.
43
STATUS OF SEISMIC RE-EVALUATION AND XA0100501 UPGRADING OF KANUPP
HAMID MAHMOOD